Direct viewing storage tubes having ceramic spacers between collector electrode and storage grid



8, 1964 E. ZIEMER ETAL ,7

DIRECT VIEWING STORAGE TUBES HAVING CERAMIC SPACERS BETWEEN COLLECTORELECTRODE AND STORAGE GRID Filed Jan. 15, 1962 \1 M 1 42 38-92 z' m laI6 fi\ f /.r/////.'/.'/, I u 4s 7 I F|g.2. Z Z

use g "t Fig.4. Fig.3.

INVENTORS Eric Ziemer,Fronk E Whittle L 0nd Augustus Miele m ra 1 ATTORNEY United States Patent 3,160,773 I DIRECT VEEWING STORAGE TUBESHAVINQ E= RAB EC SlACERS BETWEEN CQLLEQTOR ELE- TRGDE AN 1) STGRAGE GRIDEric Zierner, Horseheads, and Frank F. Whittle, Elmira, N.Y., andAugustus Miele, Canoga Park, ilali'b, assign= ors,to'WestinghouseElectric Qorporation, East Pittsburgh, Pa a corporationof Pennsylvania Filed Jan. 15, 1962, Ser. No. 166,047 5 Claims. (Cl.313-68) This invention relates to cathode ray tubes and moreparticularly to improvements for mounting the storage surface grid andthe collector electrode in direct view storage tubes.

Direct viewing storage cathode ray tubes for storing the signal imagefor direct viewing are well known. In addition to the usual luminescentscreen and writing gun, or guns, of the conventional cathode ray tubes,such storage tubes include a storage screen, a secondary electroncollimating system and a reading or viewing gun.

In general, the storage grid is a'dielectric material deposited on afine metal mesh called the backing electrode. This backing electrode isusually mounted between the collectorelectrodeand the luminescentscreen. In operation, this storage grid is charged to a uniformpotential which is very near the viewing gun cathode potential. Thewriting gun scans the storage screen and creates a charge pattern on thesurface of the storage grid by secondary emission from the dielectricmaterial of the storage screen. Because this dielectric material is anexcellent insulator, the charge pattern does not leak away, but remainsfor a long period of time. The secondary electrons liberated from thestorage surface are attracted to the collector electrode which is a veryfine metal mesh pervious to electrons from the two types of guns.

The reading or viewing gun does not scan the target system, which inthis case includes the collector electrode,

the backing electrode, the storage grid and a luminescent viewingscreen, but instead it produces a wide angle beam of electrons whichfloods the entire target system and penetrates through the holes in thecollector electrode and storage grid to bombard the luminescent viewingscreen.

The charge pattern written upon the storage screen con trols theelectrons from the viewing gun beam in a manner similar to the controlof plate current by the signal applied to the control grid of aconventional triode vacuum tube. In this way the signals applied to thewriting guns are converted to patterns on the storage screen and theseproduce corresponding patterns of luminescence on the viewing screen.The penetration of electrons through the storage grid is proportional tothe charge written upon it and accordingly the shades of gray and halftones may be faithfully reproduced. In such tubes it is desired that thedisplay be extremely bright and accordingly, a very high potential isapplied to the viewing screen, which produces a very high electroncurrent density.

It should be readily apparent from the previous general description thatthe components of the target system must be held immovably with respectto each other and with respect to the collimating flood grid and theelectron beams from the writing and viewing guns. At the same time thevarious electrodes, including the backing electrode and the collectorelectrode must be insulated from each other to withstand the highvoltages involved.

l-leretofore in maintaining the proper spacing and'the insulationbetween these electrodes, glass materials were used for insulation in atype of mounting support that necessitated the use of metal parts havingsubstantially the same'coefficient of expansion as that of the glassinsulating material. All such materials which have the propercoefiicient of expansion are usually magnetic and this adverselyaffected the path of some of the electrons,

3,160,773 Patented Dec. 8, 1964 "Ice provide a novel and improved meansfor mountingthe' storage screen in the proper relation to the othercomponents of the storage tube.

A more specific object is to providea novel and improved means formounting the storage surface grid on the collector'electrode support,which improved mounting will be simple, rugged, inexpensive tomanufacture, and will lend itself'to flexibility in varying thelength'of the mounting and will be especially adaptable to massproduction techniques.

The novel features that are considered characteristic of this inventionare set forth with particularity in'the appended claims. The inventionitself, however, both as to its organization and method of operation as'well asadditional objects and advantages will best beunderstood from thefollowing description when read'in connection with the accompanyingdrawing, in which:

FIGURE 1 is a'schematic representation,partially in section, of acathode ray storage tube in acco'rdancewith the present invention;

FIG. 2 is a partial side elevational View, partly in section, of acathode ray tube in accordance with them vention;

FIG. 3 is an enlarged end'view of a spacer mountingfor the storagesurface grid; and,

FIG. 4 is a portion of the electrode grid assemblies, showing anenlarged side view, partly in section, of one of the spacers.

Briefly, the present invention resides in the novel and improved meansfor mounting the fine wire mesh, which is called the backing electrodeand carries the storage surface, in the form of a novel ceramic-tabsub-assembly constituting an eflicient insulator andmounting support formounting the backing electrode, on the collector electrode assembly. Thestorage surface grid is a dielectric material deposited on the backingelectrode in the form of a dielectric grid. The tabs on the ceramic-tabsub assembly provide convenient means by which the subassembly can besecured to the collector electrode assembly and the backing electrode.The subassembly reduces the number of assembly operations on the mainassembly line since these subassembly units can be made as a separateassembly operation devoted entirely to this subassembly. Thissubassembly unit then becomes one of the components which is added onthe main line. One of the tabs is first welded to the collectorelectrode after which the other tab is welded to the backing electrodeto provide a very rugged and accurately dimensioned mount, ing support.7

In the embodiment of the invention illustrated in the drawings, adirect-viewing storage tube in accordance with the present inventioncomprises an evacuated'em velope =14) having a neck portion, disposedasshown in FIG. 1, housing two electron writing electron guns 12 eachhaving a cathode 14, a signalinput grid 16, a first anode 18, a secondanode 22, a focusing grid 24 and defiection plates 26. These writingguns are similar to those in electrostatically focused and deflectedoscilloscope tubes. They are capable of forming a well defined beamhaving high current density for providing high resolution and fastwriting speed. The deflecting systems for these guns is energized byappropriate beam deflecting control signals in conventional manner tocause the electron beams to trace rasters on the collector electrode 28.The elec: trode '28 is pervious to the electron beams and is disposedbetween the cathodes of the guns and the viewing screen 32. The backingelectrode 34 is interposed between the collector electrode 28 and theviewing screen 32.

stitutes the backing electrode 34. The backing electrode 34 and thestorage surface griddfi are also pervious to the electron beams.Initially, this storage surface grid 48 is charged to a uniformpotential approximately that of the potential of the viewing or floodinggun cathode -38. The storage surface grid 43 especially cooperates withboth of the writing guns l2 and the viewing gun 36in 'a special manner;the writing guns scan the storagesurface grid and create a chargepattern by a secondary emission from the storage surface and theelectron emission from the viewing gun transfers this charge pattern tothe viewing screen 32 in the form of a video image. 7

Since this dielectric storage surface grid 48 is an excellent insulator,the charge patterns do not leak away read- 14, and that potentialisapproximately the same as'the potential of the storage surface grid 48,and since the potential of the viewing screen 32 is of the order of10,000 volts, it is necessary to have means for providing the necessarymechanical support and the electrical insulation between the collectorelectrode 23 and the backing electrode 3.4. The present inventionprovides such a non- 'magnetic mounting support which has also very highelectrical insulating qualities in the form of the ceramic-tab ily, butremain there for some time. The secondary electrons liberated from thestorage surface grid 43 are attracted to the collector electrode 28. Aspreviously mentioned, the viewing gun 36 does not scan the viewingscreen 32'as do the writing guns, but on the other hand produces a wideangle beam of electrons which floods? the entire area of the storagesurface grid 4%. The electrons penetrate through the holes in the meshesof the collector electrode 28 and the backing electrode 3410 bombard theluminescent layer of the viewing screen 32. The charge pattern writtenupon the storage surface grid 43 by the writing guns 12, acting eitherjointly or individually, controls the electrons from the viewing guncathode 38 in a manner similar to the control of plate current by thesignal applied to the controlgrid of an ordinary triode vacuum tube. Inthis way the signals supplied to the two writing guns 12 through thesignal input grids 16 are converted to charge patterns on the storagesurface 48 and these produce corresponding video images on the viewingscreen 32. The number of electrons which pass through the storagesurface grid 4d is proportional to the charge written upon it by thewriting guns 12 and accordingly the variations in the incremental areacharges of the charge pattern are faithfully reproduced as a video imageon the viewing screen 32.

One of the exacting requirements of the system neces- I sary to providea sharp and crisp video image on screen 32 is that all of the electronsfrom the viewing gun 36 strikes the storage surface grid 48 at rightangles thereto.

This is necessary so that the electrons will have energy components inpaths normal to the storage surface grid.

The control grid 42, the accelerating grid' z and the collimating grid46, which is a conductive coating applied to the inside of the envelopewall, as well as the collecting electrode 28 cooperate to orient theelectrons from the viewing gun '36 so thatthey strike the storagesurface grid 48 normal thereto. The electrons from the cathode 38 oftheviewing gun are highly divergent as they emerge from the aperture ofthe. grid 44, but by properadjus ment of the potential on thecollimating grid 46, the col lector electrode mesh 28 and the backingelectrode 34, the electron stream is collimated to provide a uniformnormal flooding of the backing electrode 34. Only under operatingconditions when the paths of the electrons are normal to the backingelectrode 34 and the storage surface grid 48 will equal charges atvarious points on the storage surface grid 48 have equal control of theflood beam. From the above, it will be' seen that it is highly desirablethat there not be any magnetic material in the vicinity of the collectorelectrode mesh, storage surface grid ed, the backing electrode and theviewing screen'32 to interfere with the flow of electrons.

Also, since the writing gun cathode 38 is approximately minus 2400volts'with respect to the viewing gun cathodes subassemblies shown indetail in FIGS. 3 and 4.

The collector electrode and the storage surface grid I assembly 54comprises an annular sleeve 56 having resilient centering tabs 58. Thesetabs are suitably secured toflthe outer surface of the sleeve 56 andextend outwardly, having outer portions substantially concentric withthe sleeve which are adapted to engage the inside surface of the glassenvelope in an area beyond the col limating grid 46. Only one centeringtab 58 is shown in FIG. 2, but it should be understood that additionalthe pairs of tabs is welded to an annular metal ring 72 which forms thesupport for the backing electrode 34. The radial depth of the metal ring72 is about the same as the combined thickness of the flange 62 on thesleeve 56 plus the radial depth of the flange 62, which is substantially the same as the width of the tabs 66 shown in FIG. 3. Thecollectorelectrode 28, the backing electrode $4 with the storage surfacegrid 48 and the viewing screen 32 may be considered to be the'ta'rgetassembly for the storage tube. As clearly shown in the drawings thecollector electrode23is nearest the electron guns of the tube and thebacking electrode-34, with the storage grid, is interposed between thecollector electrode and the viewing screen 32.

The ceramic-tab assemblies 52 constitute the means for supporting thebacking electrode 34 and the storage surface grid 48 on the sleeve 56 atthe same time providing efiicient high potential electrical insulationbetween the storage surface grid 48 and the collector electrode 28.

The ceramic-tab assemblies 52'include ceramic blocks, preferablycylindrical in shape, the ends of which are provided with a metalliccoating 68 a few thousandths of an inch thick of molybdenum manganese.The coat ing 68 is applied by'paintingthe surface of the ceramic blocks.The ceramic blocks are porous so that the coating 68 penetrates theblock to provide a roughened surface which is'interlocked with theinterstices of the block. To these coatings 63 on the opposite end ofthe blocks is brazed the tabs 66 of a'copper-silvereutectic alloy.lnorder to avoid damage to the pervious electrodes from weiding'orbrazing splatter, a nickel slurry is applied to the parts being joinedbefore the brazing operation to reduce the brazing temperature required.These tabs 68 constitute convenient attaching members which can beconveniently attached by brazing or welding to the attaching members,such as the metal rings 64 and 72. The ceramic-tab assemblies 52 greatlyfacilitate the assembly operationfor assemblingthe collector electrode28, thebacking electrode 34 and the storage surface grid 58 in apredeterminedrelation to very close tolerances.

any desired length, which feature lends itself to the inexpensivemanufacture of devices such as electronic storage tubes. The subassemblyunits can be made on a separate assembly line and then assembled withthe other components of the storage tube on the main assembly line witha minimum amount of interference with the operations on the mainassembly line, thus minimizing the down time of the main assembly line.Since the units 52 can be made up as a separate operation apart from themain assembly line they can then be Welded to the collector electrodeassembly and then during the final assembly operations the backingelectrode support ring can be welded to the ceramic-tab subassemblyunits.

It will be apparent from the above description that the presentinvention provides a novel and improved method and means for applicationto a storage tube by which the backing electrode and storage grid can bemounted directly on the collector electrode assembly in a predeterminedspaced relation to very close tolerances. The tabs on the novel supportunits made of eutectic alloy make it possible to conveniently attach thetabs on one side of the support units to the collector electrodeassembly by brazing or welding and then bringing the backing electrodeand storage grid assembly into the proper spaced relation determined bythe length of the support units after which the tabs on the other sideof the supporting units are welded or brazed to the backing electrodeassembly.

While the invention has been shown in but one form, it will be obviousto those skilled in the art that it is not so limited, but issusceptible of various changes and modifications without departing fromthe spirit and scope of the invention.

We claim as our invention:

1. A direct-viewing electronic storage tube, a collector electrodehaving a supporting metal ring, a storage surface grid and a viewingscreen, said collector electrode and said storage surface grid beingpervious to electrons, said storage surface grid comprising a coating ofdielectric material on a metal wire mesh backing electrode also perviousto electrons and having a supporting metal ring, said storage surfacegrid being disposed between said collector electrode and said viewingscreen, said collector electrode being mechanically supported on a 2. Adirect-viewing electronic storage tube com-prising an evacuated glassenvelope, a source of electrons, a target assembly including a collectorelectrode, a storage surface grid, a backing electrode and a viewingscreen, said collector electrode being pervious to electrons, saidstorage grid surface being pervious to electrons and comprising acoating of dielectric material deposited on said backing electrode, saidstorage grid surface and said-backing electrode being disposed betweensaid collector electrode and said viewing screen, said collectorelectrode including a metal ring supported on a metal cylinder mountedin the end of said envelope adjacent said viewing screen, said backingelectrode including a metal ring, said backing electrode beingmechanically supported on said sleeve and electrically insulatedtherefrom by a plurality of ceramic-tab supporting units comprising: ce-

ramic blocks, a pair of metal coatings having one of their respectivesurfaces attached to said blocks by engagement with the interstices ofthe surface of the block, metal tabs brazed to each of said coatings,one of said tabs being welded to the ring of said collector electrodeand the other of said tabs being welded to the ring of said backingelectrode.

3. A target assembly for an electronic storage tube having an outerglass envelope, said assembly comprising, a metal cylindrical sleevehaving an inwardly extending flange, said sleeve adapted to be supportedon resilient tabs atfixed to the outer surface of said sleeve andengaging the inner surface of said glass envelope, a collector electrodeincluding a fine metal mesh pervious to electrons and having an annularmetal ring welded to said flange of said sleeve, a storage surface gridpervious to electrons and comprising a dielectric material deposited ona metal mesh and having an outer annular metal ring, said second metalmesh being mounted upon and insulated from said cylindrical sleeve by aplurality of units comprising electrical insulation blocks having aporous surface, a pair of metal coatings on said blocks having aroughened surface interlocked with the interstices of the surface ofsaid insulation blocks, a pair of metal tabs brazed respectively to saidcoatings on said blocks and having only portions thereof fixed to saidcoatings, one of said tabs of said pair being welded to said first ringand the other tab of said pair being welded to said second ring.

4. A target assembly for an electronic storage tube having an outerglass envelope comprising, a cylindrical sleeve having an inwardlyextending flange, said sleeve adapted to be supported on resilient tabsaifixed to the outer surface of said sleeve and engaging the innersurface of said glass envelope, an electron pervious collector electrodehaving an annular metal ring welded to said flange, a storage surfacegrid comprising dielectric material deposited on a metal mesh having anouter annular ring, said second ring being mounted upon and insulatedfrom said first ring by a plurality of units comprising porous ceramicinsulation blocks having a porous surface, metal coatings on saidindividual blocks, said metal coatings being a eutectic all'oycomprising copperand silver and having a roughened surface interlockedwith the interstices of the porous surface of said insulation blocks andthe other surface being coated with a nickel slurry, first and secondmetal tabs having portions brazed to the respective coatings on saidblocks said first tab being Welded to said first ring and said secondtab being welded to said second ring."

5. A direct viewing electronic storage tube comprising a collectorelectrode in the form of "a mesh andhaving a supporting metal ring, astorage surface grid, said storage surface grid comprising a meshandhaving a supporting metal ring,"said collector electrode being spacedfrom said storage grid by a plurality of ceramic tab support members,each of said ceramic tab members comprising a ceramicblock member, apair of metal tabs brazed to said'ceramic block members, one of saidpair of tabs welded to the supporting ring for said collector electrodeand the other of said pair of tabs welded to the supporting ring of saidstorage electrode.

References Cited in the file of this patent UNITED STATES PATENTS 7Hunter Mar. 1, 1960

5. A DIRECT VIEWING ELECTRONIC STORAGE TUBE COMPRISING A COLLECTORELECTRODE IN THE FORM OF A MESH AND HAVING A SUPPORTING METAL RING, ASTORAGE SURFACE GRID, SAID STORAGE SURFACE GRID COMPRISING A MESH ANDHAVING A SUPPORTING METAL RING, SAID COLLECTOR ELECTRODE BEING SPACEDFROM SAID STORAGE GRID BY A PLURALITY OF CERAMIC TAB SUPPORT MEMBERS,EACH OF SAID CERAMIC TAB MEMBERS COMPRISING A CERAMIC BLOCK MEMBER, APAIR OF METAL TABS BRAZED TO SAID CERAMIC BLOCK MEMBERS, ONE OF SAIDPAIR OF TABS WELDED TO THE SUPPORTING RING FOR SAID COLLECTOR ELECTRODEAND THE OTHER OF SAID PAIR OF TABS WELDED TO THE SUPPORTING RING OF SAIDSTORAGE ELECTRODE.